The invention relates to a system for providing audio signals from an auxiliary source to a radio receiver, particularly a vehicle radio receiver, using a wireless link. The invention further relates to a method of providing audio signals to a radio receiver by automatically selecting a number of low noise radio frequencies for wireless signal transmission from the auxiliary source to the radio receiver and providing user controls to select one of the frequencies for transmission.
A number of systems exist which use an existing audio system in a vehicle for playback of audio signals from a compact disc (CD) player, tape cassette player, satellite broadcast receiver, or other auxiliary audio source. These existing systems are designed to play back the signals from the auxiliary audio source using a number of different methods. For example, one system receives satellite broadcast signals and provides them to the optical head of a CD player, or the magnetic head of a tape cassette player, already installed in the vehicle. This system is disadvantageous because it requires the user to install a removable adapter to couple the satellite broadcast signal to the optical or magnetic head of the vehicle audio system.
In other systems, signals from an auxiliary audio source such as a CD or cassette player are coupled to a vehicle radio receiver via a wireless link such as an FM wireless link. In one system, for example, signals from the auxiliary audio source are frequency translated to the FM frequency band and are then broadcast from a transmitter in the vehicle on several fixed frequencies for reception by the vehicle radio receiver. A user then selects one of these frequencies on the vehicle radio receiver to listen to the transmitted signals. In another system, a user first selects a radio frequency in the FM band that is not being utilized in the local area, and then tunes the existing vehicle radio receiver to the selected frequency. The user then tunes a transmitter in the vehicle to the same frequency. The transmitter receives a signal from a CD player and transmits the signal at the selected frequency.
The two types of wireless FM systems described above are disadvantageous because they do not provide for automatic monitoring of the radio frequencies used for retransmitting signals from the auxiliary audio source via the wireless link to the existing vehicle radio receiver. The radio frequencies selected by the user, or the fixed frequencies used by the transmitter, may be subject to interference and poor signal quality. In addition, the manual selection of a suitable radio transmission frequency is inconvenient to users.
A need therefore exists for an audio coupling system that overcomes the aforementioned drawbacks of the existing systems. Specifically, a need exists for a radio frequency or RF-coupled satellite broadcast receiver for vehicles which provides a wireless link to an existing vehicle radio receiver. In addition, a need exists for an RF-coupled satellite broadcast receiver for vehicles which automatically selects optimal radio frequencies for wireless transmission to the vehicle radio receiver.
In accordance with one aspect of the present invention, an RF-coupled satellite broadcast receiver is provided which scans a radio frequency (RF) band in which a radio receiver, preferably but not necessarily in a vehicle, can be tuned for signal reception. The RF-coupled satellite broadcast receiver selects at least one open RF channel having the lowest noise floor for retransmission of the received satellite broadcast signal to the radio receiver.
In accordance with another aspect of the present invention, the RF-coupled satellite broadcast receiver selects a plurality of open RF channels having low noise floors and is capable of retransmitting the received satellite broadcast signal on any of these available RF channels. The available RF channel information is provided to the user. The user selects one of these channels and then tunes the vehicle radio receiver to the selected channel to listen to the satellite broadcast program.